17-year-old Olga Danilovic defeated fifth seed Aliaksandra Sasnovich 6-2, 5-7, 7-5 to reach the final of the Moscow River Cup, extending her incredible run at the competition.
Danilovic only qualified for the main draw as the lucky loser but has now beaten Sasnovich, eighth seed Kaia Kanepi and top seed Julia Goerges to reach the first final of her career.
The Serbian was 5-2 up in the third and final set but Sasnovich, the world No. 42, rallied to bring it back to 5-5. Danilovic immediately broke back, eventually serving out to win the match in two hours and 19 minutes.
She will now face Russian Anastasia Potapova, also 17, in an all-teenage final on Sunday.
Potopova, the 2016 Wimbledon girls' singles champion, advanced after her opponent, Tamara Zidansek, retired in the third set of the earlier semifinal, with the Russian leading 3-6, 6-4, 5-2.